Variable walking foot apparatus for a sewing machine for mattresses

ABSTRACT

A method and apparatus for forming a partial mattress sack which prevents radial bunching of the mattresses. The method includes the steps of feeding first and second panels having different edge lengths at different rates through a sewing machine to form the partial mattress sack. The apparatus includes a variable speed upper walking foot having an automatic speed adjustment.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.08/210,582, filed Mar. 17, 1994 now U.S. Pat. No. 5,526,761, andentitled "Method and Apparatus for Closing Mattresses."

FIELD OF THE INVENTION

This invention relates generally to a method and apparatus for closingmattress sacks and, more particularly, to an apparatus for closingmattresses having a variable walking foot for gathering an edge of a toppanel to be longer than the edge of a side panel.

BACKGROUND OF THE INVENTION

Modem mattresses generally include an inner construction, covered by amattress sack. A mattress sack is formed from a top and bottom panel anda side panel, joining the top and bottom panel. Finished mattresses aregenerally heavy and bulky. This weight and bulk has a direct impact onmanufacturing cost, because the weight and bulk are more likely to causeinjury, for example. In addition, existing and future governmentregulations ("OSHA" regulations, for example) have provisions concerningthe number of people necessary to flip mattresses.

While mattress manufacturers desire lower cost manufacturing processes,they also demand a product with high quality sizing. For example, it isgenerally understood that it is relatively simple to attach a top panelof a first peripheral length and side panel having a same length edge.However, such a construction produces an unacceptable product. This isso, because the final construction is susceptible to unsightly "radialbunching" of the side panel when the mattress is loaded, for example bya person sitting on the mattress (radial bunching refers to the effectproduced when the side panel bunches outwardly and radially). To avoidbunching, mattress manufacturers attach the top and bottom panels of afirst peripheral length with a side panel having a shorter edge length.This operation, however, has been performed manually with skilled labor,which increases the manufacturing costs. In such operations, a skilledoperator pulls on the side panel, while pushing and manipulating the toppanel to fit the two together. This is usually done with known tape-edgeclosing machines having a sewing machine and track mechanism. Theoperator follows the machine around the periphery of the mattress firstmanually fitting the side panel and top panel in conjunction with themachine. Then, the mattress is flipped, and the operator follows themachine around the periphery of the mattress manually fitting the sidepanel and bottom panel. As a result, the skilled fitter is needed to fitboth edges, i.e., the top and side, and the bottom and side.

Accordingly, it is an object of the invention to provide a method andapparatus for forming partial sacks having a top panel with a peripheraledge length and a side panel with a shorter edge length so that manualfitting need be done for one edge only.

SUMMARY OF THE INVENTION

These and other objects are achieved in accordance with the presentinvention. The present invention includes a conventional sewing machinewith certain modifications, described below, that allow a top panel (ora bottom panel) of a first edge length to be joined with a side panel ofa second edge length. Consequently, a partial sack may be formed. Theinner construction is then placed in the partial sack, and then a bottom(or top) panel is attached.

In a preferred embodiment, the conventional machine implements a knownso-called safety stitch. The machine includes a high lift feedingmechanism to allow thick materials to be joined. The feeding mechanismis constructed of an upper feed foot and a lower feed foot. The upperfoot grabs a top (or bottom) panel, and the lower foot grabs the sidepanel. Modifications are made to the feeding apparatus of theconventional machine to implement a variable overfeed. In particular,the bottom feed operates at a fixed rate, and the top feed operates at arate that is adjustable. The overfeed receives the top (or bottom) panelat a first rate and the side panel at a second rate. The ratio of thetwo rates corresponds to the ratio of the two lengths. The overfeedmechanism is controlled by the user so that different rates of overfeedmay be conveniently selected. The control is responsive to user inputsand a foot pedal.

Another aspect of the invention includes a drag mechanism in the feedingpath of the side panel to provide a drag to the side panel that isstitched to the top (or bottom) panel. The drag mechanism ispneumatically controllable by the user.

In a further aspect of the invention, a conventional Singer 300W 194sewing machine is modified to include an upper walking foot to providethe desired overfeed of the top (or bottom) panel. The existing upperand lower feed dogs and the presser foot are retained, and movement ofthe upper walking foot mechanism is coordinated with the movement of theother components to provide the overfeed. The upper walking foot gathersthe material of the top (or bottom) panel prior to the needle in thefeed direction while the presser foot holds the top (or bottom) and sidepanels stationary at a location after the needle in the feed direction.The amount of overfeed is varied through a servo motor which adjusts thelocation of one of the linkages along a banana slide to change the speedand throw of the upper walking foot.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully appreciated from the following detaileddescription when taken in conjunction with accompanying drawings, inwhich:

FIG. 1 is a perspective, topside view of one apparatus according to theinvention;

FIG. 2 is a simplified side view of the sewing machine of FIG. 1 inpartial cross-section illustrating the presser foot biasing structure ofthe present invention;

FIG. 3 is perspective view illustrating a trapezoidal wedge used toincrease the clearance of the needle, presser foot and upper walkingfoot of the sewing machine of FIG. 1;

FIG. 4 is side view illustrating the relative relocation of the needleaccomplished by the insertion of the wedge shown in FIG. 2 in the sewingmachine of FIG. 1;

FIG. 5A is a simplified cutaway side view of the mechanism for operatingthe presser foot, needle, and walking feet of the sewing machine of FIG.1 when the machine is in a first condition;

FIG. 5B is a simplified, cutaway side view of the mechanism foroperating the presser foot, needle, and walking feet of the sewingmachine of FIG. 1 when the machine is in a second condition;

FIG. 6 is a detailed perspective view of the lower walking feet andwalking feet mechanism of FIGS. 5A and 5B;

FIGS. 7A and 7B are simplified cutaway side views showing the mechanismfor driving the needle drive shaft of the sewing machine of FIG. 1 attwo different instances during the drive cycle;

FIG. 8 illustrates a presser foot and top feed of the apparatus of FIG.1;

FIG. 9 is a perspective view of the lower walking foot of the apparatusof FIG. 1;

FIG. 10 illustrates a pneumatic system of the apparatus of FIG. 1;

FIG. 11 is a partially cutaway perspective view of the apparatus of FIG.1;

FIG. 12 is a diagram illustrating the structure of a conventionalmattress sack;

FIG. 13 is a perspective, side view of another sewing apparatus inaccordance with the present invention;

FIG. 14 is a detailed, perspective view of the upper walking footmechanism of the sewing apparatus of FIG. 13;

FIGS. 15A, B, C and D are side, diagrammatic views of certain componentsof the sewing apparatus of FIG. 13 illustrating their relative positionat different stages oft he sewing process; and

FIG. 16 is a top diagrammatic view showing the relative positions of thecomponents of the apparatus of FIG. 13, in conjunction with the mattresspanels being sewn.

DETAILED DESCRIPTION

Certain features of this invention were described in a commonly owned,co-pending U.S. patent application, Ser. No. 07/854,373, which isspecifically incorporated herein by reference. In particular,application Ser. No. 07/854,373 discussed certain modifications to anovercast Atlanta, Ga. This application, on the other hand, relates tocertain other modifications to the model 515-4-26 machine to implement ahigh lift safety stitch. In addition, the present invention relates to amethod of employing the modified model 515-4-26 machine to form apartial mattress sack. The machine, as modified, requires less labor toproduce a partial sack having a side edge length less than theperipheral edge length of the top panel so that the sack is lesssusceptible to radial bunching and the like.

FIG. 1 is a perspective view, illustrating stitcher 200, receivingbinding tape 210, and top panel 205 in relation to surface 211. The sidepanel 206 is received underneath and is shown more particularly in FIG.11.

A tape folder 220 of conventional design folds tape 210 so that tape 210may be placed around the respective edges of the top panel 205 and sidepanel 206. Stitcher 200 then joins the tape 210, top panel 205, and sidepanel 206 with a so-called "safety stitch." The mechanisms forperforming a safety stitch are well known and will not be discussedherein except to the extent that they are material to a description ofthe invention.

FIG. 2 is a simplified side view, in partial cross-section, of anexemplary mechanism for causing the presser foot 12 of a sewing machineto reciprocate in vertical motion to clamp the material to the throatplate when the needle is in the material and to rise and release thematerial when the needle exits the material so that the material can beadvanced by walking feet before the next stitch. The presser foot 12 ispermanently biased downwardly by a biasing mechanism 10.

Floor 26b of cap nut 26 defines the downwardmost position of presserfoot arm 14 and thus presser foot 12. The spring lengths and spacerlengths are chosen such that the springs are at least slightlycompressed when transverse flange 14a of rod 14 is in its downwardmostposition in which flange 14a abuts against the floor 26b of bottom capnut 26. A cushioning member such as polyurethane pad 34 is attached tothe inner surface of floor 26b so as to cushion the impact of flange 14aagainst the floor 26b.

Longitudinal flanges 28a, 30a, 30b and 32a of the spacers 28, 30 and 32assist in preventing the springs from bending since they extend throughthe center of the helical springs. Accordingly, the longitudinal flanges28a, 30a, 30b and 32a should be as long as possible.

The length of the flanges, however, is limited by the uppermost possibleposition of rod 14. That is, for instance, if the spring is compressedenough, the top part of flange 28a will hit the bottom part of flange30b. Accordingly, these flanges must be short enough such that they willnot prevent the rod 14 from reaching what would otherwise be itsuppermost possible position.

Since upper cap nut 24 can be easily removed from the tubular housing byunscrewing it, preload spacer 32 can be replaced quickly with a spacerof a different length when it is desired to change the downwardcompressor force of presser foot 12 as, for instance, may be the casewhen significantly changing the thickness of the material which is beingsewed. As the material becomes increasingly thicker, the downwardpressure of presser foot 12 on the material increases because the springwill be compressed more when presser foot 12 is resting on top of thematerial. Accordingly, in such a situation, if the force is too great,preload spacer 32 can be replaced with a shorter preload spacer thusreducing the compression of the springs. In fact, since upper cap nut 24is removable the springs themselves can be easily replaced if desired.

Further, the lower travel limit of presser foot 12 is limited by theposition of floor 26b of lower cap nut 26 and the thickness ofpolyurethane pad 34. Accordingly, by proper positioning of floor 26b,presser foot 12 can be prevented from crashing into the throat plate 11,thus reducing wear of the components of the machine. Since lower cap nut26 is engaged to housing 22 by thread means, the height of floor 26b canbe adjusted by screwing or unscrewing lower cap nut 26 to the desiredextent.

Means are provided for manually lifting the presser foot 12 (and upperwalking foot) prior to operation in order to initially insert thematerial to be sewed in the throat of the machine. A hydraulic cylinder29 can be manually operated to raise the presser foot 12. Shaft 31 iscoupled to presser foot connecting member 14 via arms 33 and 35.Connecting member 14 may be a cylindrical rod. Upon activation, shaft 31is extended out of hydraulic cylinder 29 causing arm 33 to rotatecounter-clockwise about pivot 41 thus lifting arm 35. End 35b of arm 35extends below a flange 14c on rod 14 and lifts presser foot rod 14 andpresser foot 12 by exerting an upward force on flange 14c. Arm 35 isslotted at 35a. A pin 43 is fixedly attached to a wall behind arm 35 andextends through slot 35a. Thus, arm 35 can slide up and down and rotateabout pin 43. As will be explained in greater detail with respect toFIGS. 5A and 5B, the upper walking foot is coupled to rod 14 vialinkages 42 and 162 such that the lifting of presser foot rod 14 alsolifts the upper walking foot. During a sewing operation, the presserfoot 12 is urged upwardly at fixed intervals by a reciprocating driveshaft 36 as will be described in greater detail herein.

The presser foot 12 is coupled to connecting member or rod 14 by meansof a presser foot arm 16. Rod 14 is biased downwardly by biasing meanssuch as helical die springs 18 and 20 contained in tubular housing 22.Housing 22 includes upper cap nut 24 and lower cap nut 26. The ends ofhousing 22 are externally threaded so that the internally threaded capnuts 24 and 26 can be screwed onto the opposing ends of housing 22. Roof24a of upper cap nut 24 is solid. Floor 26a of lower cap nut 26comprises an opening 26b through which rod 14 slidably travels. Theupper portion of rod 14 includes a transverse flange 14a which is widerthan opening 26b such that the flange cannot pass through hole 26b,thereby trapping the upper portion of rod 14 within the presser footbiasing mechanism 10. A longitudinal flange 14b extends upwardly fromrod 14 and fits within a slot in spacer 28. Spacer 28 includes alongitudinal flange 28a which extends upwardly through the center ofhelical spring 23. A second spacer 30 is positioned between helicalsprings 18 and 20 and has opposing flanges 30a and 30b extendingtherefrom through the centers of springs 18 and 20, respectively. Apreload spacer 32 is positioned between the upper end of spring 18 androof 24a of upper cap nut 24. Longitudinal flange 32a extends frompreload spacer 32 through the center of helical spring 18.

FIG. 3 illustrates another aspect of the improvements made to thePegasus machine. FIG. 3 is a perspective view of the sewing machineillustrating the trapezoidal wedge 50 used to increase the throatclearance of the sewing machine. Wedge 50 is also shown in cross-sectionin FIGS. 7A and 7B. In accordance with the present invention, wedge 50is inserted between the needle housing 52 and the main housing 54. Theneedle guide shaft, the hollow tubular shaft through which the needletravels, as well as the needle drive shaft 36 are fixedly attached tothe upper housing. The needle guide shaft does not appear in FIG. 3, butis shown in FIGS. 5A and 5B and is designated with reference number 81.The raising and tilting of needle housing 52 by the insertion oftrapezoidal wedge 50, thus raises and tilts the needle.

As illustrated in FIG. 4, in the original Pegasus sewing machine, theneedle is angled from the vertical by approximately 20°. Thus, if theheight of the needle is raised without changing the angle of the needle,the needle will travel in a path along line 5 in FIG. 4 parallel to itsoriginal path along line 3 but displaced therefrom by a predetermineddistance perpendicular to the original path. The upper travel limit ofthe needle tip (as well as the lower travel limit) is raised by height hin FIG. 4. However, if the angle of the needle is not changed, theneedle will not meet the spreader or the looper in the originallocations. The shift in the needle path is not too significant withrespect to meeting with the looper. The looper typically has a fairlylong horizontal throw and will still be able to catch the thread off ofthe needle, particularly if the throw of the needle is increased so thatthe lower travel limit of the needle is not significantly changed in thevertical direction from the original needle path.

However, the relative position of the needle and spreader when they areto exchange thread must be maintained to a fairly high tolerance. Aswill be described herein in greater detail with respect to FIGS. 8A and8B, the path of the spreader has also been modified in the presentinvention such that the spreader should now meet the needle at point 62as opposed to point 61. As shown in FIG. 4, point 62 would not be on thepath traversed by the needle if its angle was not changed. In order tocause the needle to still meet with the spreader within acceptabletolerance limits, the angle of the needle must be reduced about 4° fromthe vertical. Accordingly, the side cross-section of wedge 50 (as shownin FIGS. 7A and 7B) instead of being square, is trapezoidal, with theupper surface 50a angled about 4° relative to the bottom surface 50b.

FIGS. 5A and 5B are simplified cut away side views of the sewing machineof the present invention at two different stages. FIGS. 5A and 5B aregreatly simplified to ease the understanding of the invention. Forinstance, FIGS. 5A and 5B do not show the looper or the spreader. FIG. 6is a simplified perspective view of some of the components in lowerhousing 54 of FIGS. 5A and 5B. In FIG. 5A, the needle is withdrawn fromthe material and the presser foot 12 is not engaged with the material.At this moment, upper walking foot 72 and lower walking feet 74 and 76are engaged with the material and moving leftward in the figure. In FIG.5B, the needle is in the material, the presser foot is clamping thematerial down to the throat plate and the upper and lower walking feet72, 74 and 76 are not engaged with the material and are moving towardsthe right.

The desired cyclical movement of the needle, presser foot and allwalking feet will be described at first without reference to themechanical structure for causing the movement.

In general, one or more layers of material 77 are laid on the throatplate 11. Presser foot 12 is biased downwardly onto the upper surface77a of the material and presses the material against throat plate 11. Atthis time, upper walking foot 72 is in its raised position so that it isnot in contact with the material. Lower walking feet 74 and 75 are belowthe throat plate so that they do not engage the material. Presser foot12 remains pressed against material 77 as the needle 70 advances in andthrough the material 77. Near the bottom of its travel limit, when thetip 60 of the needle is below the throat plate 11, a looper (not shownin FIGS. 5A and 5B) passes closely by the tip 60 of the needle topartially complete the stitch in a manner which is known in the art.

At essentially the same moment that the needle tip 60 exits from thematerial during its upward stroke (i.e., the point where the tip 60 ofneedle 70 is even with bottom surface 12a of presser foot 12), presserfoot 12 begins to rise off of the material. Simultaneously, upperwalking foot 72 lowers and lower walking feet 74 and 76 raise to engagethe material. All of walking feet 72, 74 and 76 travel in ellipticalpaths illustrated by arrows 72a, 74a and 76a, respectively, in FIG. 5Asuch that when the walking feet are engaging the material, they aremoving in the forward direction (i.e., to the left in FIGS. 5A and 5B)and thus advance the material. Due to the elliptical motion of thewalking feet, they eventually disengage the material 77 and begintraveling rearward to be prepared to advance the material after the nextstitch. Just before the walking feet disengage the material, presserfoot 12 once again lowers into contact with the material starting thecycle all over again.

The mechanism for causing all of this action to occur at the appropriateinstances will now be described in detail with respect to FIGS. 5A, 5Band 6. Primary lower walking foot 74 is coupled via arm 80 to primarylower walking foot bar 82. Secondary lower walking foot 76 is coupledvia arm 86 to secondary lower walking foot bar 84. In the view of FIGS.5A and 5B, bar 82 is directly behind, and therefore obscured by, bar 86.Both bars can be seen in FIG. 6.

The vertical component of the motion of primary lower walking foot 74 isprovided by walking foot drive shaft 88 via arm 93 and linkage 95. Driveshaft 88 is driven to reciprocate approximately 1/4 of a revolution bymain drive shaft 167 via arms 151 and 153 and off center sub-shaft 155.This causes arm 93 to rock back and forth as illustrated by arrows 96.One end of linkage 95 is coupled to arm 93 at pivot 110 while the otherend is coupled to primary walking foot bar 82 by pivot shaft 99 which isfixedly attached to bar 82 at one end and pivotally attached to linkage95 by pivot 98 at the other end. End 102 of bar 82 comprises a slot 104through which passes a fixed guide bar 106. Guide bar 106 fixes end 102of bar 82 vertically, however, slot 104 allows bar 82 to slidehorizontally relative to guide bar 106. Bar 82 slides horizontally inresponse to the motion of the walking foot drive shaft 88 transmitted tobar 82 via arm 93 and linkage 95.

Secondary lower walking foot bar 84 is driven off of shaft 88 via asecond arm 90 and linkage 100. However, whereas in the primary lowerwalking foot mechanism, pivot 110 on arm 93 is fixed at a specifieddistance from drive shaft 88, in the secondary lower walking footmechanism, pivot point 100 connecting arm 90 to linkage 92 isadjustable. The specific mechanism utilized for adjusting pivot point100 is not shown for ease of illustration. However, it should beunderstood that mounting box 112 can be loosened and slid up or down onarm 90 and then re-tightened to fix pivot point 100 at the desireddistance on arm 90 from shaft 88. In this manner, the speed of secondarylower walking foot 76 can be changed relative to the speed of primarylower walking feet 74. This is the result of simply making the momentarms (i.e., the distance between the drive shaft 88 and the pivots 100and 110) different. For instance, if the moment arm of the secondarywalking foot is longer than the moment arm of the primary lower walkingfoot, then, for any given rotation of the drive shaft 88, pivot point100 (and thus walking foot 76) will traverse a greater distance thanpivot point 110 (and thus walking foot 74). Accordingly, secondary lowerwalking foot 76 will traverse a greater distance than primary lowerwalking foot 79 in the same period of time (i.e., it will travelfaster).

As previously noted, the motion of walking feet 74 and 76 is notstrictly horizontal but is elliptical, having a small verticalcomponent. The vertical component of the motion of lower walking feet 74and 76 is provided by off center sub-shaft 157 of main drive shaft 167.Unlike the other drive shafts discussed herein, main drive shaft 167does not reciprocate but simply rotates in a clockwise direction. Blocks147 and 149 are mounted on off center sub-shaft 157 and are positionedwithin horizontal slots 111 and 113 of bars 82 and 84, respectively. Therotation of main drive shaft 167 causes sub-shaft 157 and blocks 147 and149 to travel in circles. The vertical component of the circular motionof blocks 147 and 149 is transmitted to bars 82 and 84. The horizontalcomponent of their motion is not transmitted to the bars since blocks147 and 149 can slide horizontally in slots 111 and 113, respectively.

The horizontal component of the elliptical motion of upper walking foot72 is provided by connection of upper walking foot 72 via linkage 118and arm 120 to secondary lower walking foot bar 84. As shown in FIG. 5A,linkage 118 is pivotally coupled to arm 120 by pivot 122. The other endof arm 120 is fixedly connected to bar 84 by pivot 124. Accordingly, asbar 84 moves horizontally, so does arm 120 and, consequently, linkage118 and upper walking foot 72.

Due to the limited space available in the machine, a slot 132 was cutthrough primary lower walking foot arm 82 through which arm 120 passes.The slot is long enough to allow arm 120 to slide horizontally thereinbecause secondary lower walking foot bar 84, to which arm 120 is rigidlyattached, can move at a different rate of speed and traverse a differentdistance than arm 82, as previously discussed.

The motion of presser foot 12 and needle 70 as well as the verticalcomponent of the motion of upper walking foot 72 now will be describedin detail in relation to FIGS. 5A, 5B, 7A and 7B. Needle assembly 71comprises needle 70, which is attached to a first needle bar 140, which,in turn, is attached to a second needle bar 142 of larger diameter. Theneedle assembly 71 is driven up and down by reciprocating needle driveshaft 36 via arm 146 and linkages 148 and 150. Arm 146 is rigidlyattached to the drive shaft 36. Connection points 152 and 154 arepivots. Needle drive shaft 36 further drives presser foot 12 (upwardlyonly, since presser foot 12 is permanently biased downwardly by assembly10) via arm 38, and linkages 40 and 42. Arm 38 is fixedly mounted toshaft 36. Connecting points 144, 158 and 160 are pivoting points. Point160 is coupled to presser foot rod 14, which in turn is rigidly coupledto presser foot 12 via presser foot arm 16. Needle drive shaft 36 alsoprovides the vertical component of the elliptical motion of upperwalking foot 72 via arm 138, linkages 40, 42 and 162 and arm 118.Connections 164 and 168 are pivots.

As discussed with respect to FIGS. 2 and 3, the height of the needle 70has been increased by the addition of a trapezoidal wedge between theneedle housing and the lower housing. Consequently, the throw of needle70 had to be increased so that it still extends below the throat plateat the bottom of its throw to meet with the looper. The throw of needle70 is increased in the present invention by increasing the rotation ofneedle drive shaft 36. The driving mechanism for causing needle driveshaft 36 to rotate is not shown in FIGS. 5A and 5B. Instead reference ismade to FIGS. 7A and 7B which are side views of the needle drive shaftand selected related components. Needle drive shaft 36 itself is drivenoff of the main drive shaft 167 via connecting member 166. The bottom ofconnecting member 166 is attached to main drive shaft 167 via off-centerpivot 170. The rotation of main drive shaft 167 drives member 166 up anddown in primarily vertical motion. Needle drive shaft 36 is driven bythe vertical motion of the upper end 172 of connecting member 166 viaarm 174. Arm 174 is fixedly attached to needle drive shaft 36 andpivotally attached to connecting member 166 by pivoting connection 178.The rotation of needle drive shaft 36 has been increased in accordancewith the present invention by replacing the original arm couplingconnecting member 166 to drive shaft 36 with the much shorter arm 174.Accordingly, the same vertical travel of connecting member 166 producesa greater rotation of shaft 36. In order to accommodate the much closerproximity of the upper end 172 of connecting member 166 to needle driveshaft 36, the diameter of needle drive shaft 36 arm 174 was reduced inthe vicinity of arm 174 so as to prevent connecting member 166 fromstriking shaft 36 at the top of its motion. The original circumferenceof shaft 36 is shown by dotted circular line 175 in FIGS. 7A and 7B. Ascan be seen in FIG. 7A, when connecting member 166 is in its uppermostposition, the inner side surface 166a of connecting member 166 wouldhave contacted the needle drive shaft of original circumference(circular line 175). Accordingly, drive shaft 36 was reduced in diameterin the vicinity of arm 174 and connecting member 166 to have thecircumference illustrated by solid circular line 36a.

In FIGS. 7A and 7B, arm 146 and related components for driving theneedle as well as arm 38 and related components for driving the presserfoot are shown in phantom. It should be understood that these componentsare displaced perpendicular to the surface of the page from connectingmember 166, and arm 174 and, in the Pegasus sewing machine, are actuallyseparated from each other by a plate through which the needle driveshaft 36 passes (see FIG. 3b, for instance). It should also beunderstood that the diameter of drive shaft 36 has not been changed atthe point where arms 146 and 38 are coupled to it.

Connecting member 166 was also lengthened to accommodate for the raisingof needle drive shaft 36 by the insertion of wedge 50 between the twohousings.

Returning to FIGS. 5A and 5B, presser foot 12 is permanently biaseddownwardly by spring assembly 10 as previously described. When needledrive shaft 36 rotates in the counter-clockwise direction, an upwardforce is exerted on presser foot rod 14 by needle drive shaft 36 via arm38 and linkages 40 and 42. As can be seen in FIG. 5A, when upper walkingfoot 72 meets the upper surface 77a of the material 77, walking foot 72presses down against the material until a predetermined force is exertedand the downward force of foot 72 is cancelled out by the upward forceof throat plate 11 and material 77. At this point, the downward motionof foot 72 and thus arm 118 is halted. This, in turn, cause pivot point164 to become almost stationary (linkage 162 actually can rotate veryslightly when arm 118 is stationary). After this condition is reached,further clockwise motion of needle drive shaft 36 continues to forcepivot point 158 on linkage 42 downward. However, since point 164 isessentially fixed in space, arm 42 rotates counterclockwise around point164, thus causing pivot point 160 at the opposite end of linkage 42 torise. Pivot point 160 is coupled to presser foot rod 14. Accordingly,presser foot rod 14 (and presser foot 12) are forced upwardly todisengage the material. Accordingly, presser foot 12 does not begin totravel upwardly off of top surface 77a of material 77 until walking foot72 engages the material. The length of the various linkages and arms areselected such that the needle has also disengaged the material at thispoint so that the walking feet advance the material (to the left inFIGS. 5A and 5B) only after the needle (and presser foot) havedisengaged from the material.

Referring now to FIG. 5B, as the needle 70 plunges back into thematerial 77, a similar but opposite action occurs to that describedabove. When needle drive shaft 36 reaches the end of itscounterclockwise reciprocation, it begins to rotate clockwise againurging needle 70 downwardly via arm 146 and linkages 148 and 150. Thisclockwise rotation of shaft 36 also causes linkage 42 to begin rotatingclockwise around pivot point 164 urging presser foot 12 downwardly andeventually back into contact with the top surface 77a of the material.When the downward motion of presser foot 12 is halted by material 77,pivot point 160 at the end of arm 42 becomes fixed in space.Accordingly, at the point where the downward motion of presser foot 12is halted by contact with the material, arm 42 continues to rotate inthe clockwise direction, but it rotates about pivot point 160 instead ofpivot point 164. Accordingly, pivot point 164 now begins to rise thuslifting upper walking foot walking foot arm 118.

As noted above, needle drive shaft 36 has been raised by the addition ofthe wedge shown in FIG. 2. Accordingly, the maximum clearance of notonly the needle but also the presser foot and the upper walking foothave been increased. The maximum clearance of the presser foot 12increases as linkages 40 and 162 increase in length. Essentially,increasing the lengths of linkages 40 and 162 produces an increase inthe throw of the presser foot which translates at least partially intoan increase in its upper travel limit. The lower travel limit of presserfoot 12 is dictated by the material 77, the throat plate 11, or thelower cap nut 26 of spring assembly 10, whichever is highest.

According to a different embodiment of the invention, the modifiedmachine is further modified with known techniques to implement a safetystitch, i.e., one needle and one looper. As such, a high lift safetystitch machine may be devised so that tape edge joining and the like maybe performed. Referring to FIG. 8, an alternative presser foot 12' andtop feed 72' are shown. The foot 12' and the feed 72' are theappropriate components for a safety stitch machine.

Now referring to FIG. 9, the linkage previously discussed with referenceto FIG. 6 is shown, but with the modification that lower feed 76 and bar86 are removed with known techniques. As such, the modified machine hasone lower feed 74 only. As discussed, above this feed 74 operates at afixed rate. The upper feed 72 is still attached by arm 120 to linkagethat provides a variable feed rate, as discussed above. Consequently, anoverfeed may be implemented by repositioning pivot point 100, asdiscussed above.

Because operators may want to adjust and re-adjust the overfeed rateduring the taping application, another aspect of the invention includesa pneumatic system 300 to conveniently reposition the pivot point 100.

As discussed above, the pivot point is typically adjusted manually. FIG.10 illustrates a view of the external casing of the stitcher 200 withlever 302. Typically, a lock nut is manually loosened and lever 302 ismoved to cause the repositioning of pivot point 100 and member 90.

However, in the present invention, lever 302 is connected to pneumaticsystem 300 which has three pistons 300a-c connected in series. Eachpiston may be independently activated under user control 304 and allthree may be activated with a foot pedal 305 with known techniques.Consequently, the user may adjust the overfeed with the user control304. The desired rate of overfeed will depend on the ratio of the edgelengths and the type of the materials that are to be joined. If a userneeds "bursts" of high overfeed, he or she will likely desire toactivate the pistons 300a-c with the foot pedal.

FIG. 11 illustrates the invention in side view, in conjunction with apneumatic drag foot 305. The foot 305 has side panel 206 pass betweenits plates 305a and b. Under user control, the drag foot may introducesa variable amount of drag to the side panel 206 to keep the side paneltaut and assist in the overfeed of a top panel having a longer edgelength.

The method of forming a partial mattress sack will now be described withreference to FIGS. 1-12. The modified machine is adjusted to implement adesired amount of overfeed, which will, as discussed below, depend uponthe sizes of the panels and the types of materials used. A side panel206 is loaded into the modified machine, preferably, passing the sidepanel 206 between two drag plates 305a and 305b. The plates 305a and305b provide a variable amount of drag to the side panel to keep ittaut. A top panel 205 is also loaded into the machine. The top panel hasa first edge length, and the side panel has a second edge length, whichis shorter than the first edge length. For example, the first edge maybe 205 inches, and the second edge may be 200 inches. The two panels arethen joined around the entire peripheral edge of the top panel by themodified machine. The modified machine uses a top feed 72 which moves ata first rate, and a bottom feed 74 which moves at a second rate. Theoverfeed, i.e., the difference in feeding rates, allows a longer edgedtop panel to be fed along with a shorter side panel. Preferably, asafety stitch and tape are used to join the materials. The joined topand bottom panel form a partial sack.

Afterwards, an operator will fit the partial sack to an innerconstruction 223. A bottom panel 225 of a first length will then bejoined to the side panel 206 of the second length with a tape edgemachine or the like. This will require the skilled labor of manuallyfitting the longer bottom panel to the shorter side panel, but asreadily seen, this skilled operation is needed for one edge of the sidepanel only.

Another embodiment of an apparatus which may be used for implementingthe method of the present invention will now be described withparticular reference to FIGS. 13-16. In this embodiment of the apparatusof this invention, a Singer 300W 194 sewing machine, available fromSinger Sewing Machines of New York, N.Y., has been modified to includean upper walking foot 320 which produces the desired overfeed of theedge of a top or bottom panel of a mattress sack. The Singer 300W 194sewing machine is a machine which is conventionally used for closingmattresses, or for sewing the side panels to the top and bottom panelsof a mattress sack. Such sewing machines are well known, and need not bedescribed in detail, except to the extent necessary to provide one ofordinary skill in the art with an adequate understanding of themodifications made thereto in accordance with the present invention.

Sewing machine 300 is a modified Singer 300 194 sewing machine andincludes main drive shaft 302 mounted in housing 304, needle 306,presser foot 308, upper feed dog 310, lower feed dog 312 and throatplate 314. Needle 306 oscillates up and down, or in a directionperpendicular to the direction of feed of layers 316 and 318 (arrow 319in FIGS. 15A-B) and is driven off the main drive shaft 302 in a mannerwell known to those skilled in the art. Needle 306 oscillates in thesewing area of machine 300. Presser foot 308 likewise moves only in adirection perpendicular to the feed direction 319 and holds layers 316and 318 in place during the gathering operation, as will be described.Presser foot 308 is positioned after needle 306 in the direction of feed319 of layers 316 and 318. Upper feed dog 310 and lower feed dog 312cooperate to move layers 316 and 318 through the sewing area in thedirection of feed 319 or from fight to left as shown in FIGS. 15A-B.Upper feed dog 310 moves in a direction perpendicular to the feeddirection 319 and in the feed direction 319, as shown in FIGS. 15A-D, toadvance layers 316 and 318 from right to left as shown in FIGS. 15A-D.Upper feed dog 310 is coupled to main drive shaft 302 through cams andlinkages to produce the desired motion in a manner well known to thoseskilled in the art. Needle 306 passes through a hole in upper feed dog310 and cooperates with upper feed dog 310 and lower feed dog 312 togrip layers 316 and 318 and advance them in the feed direction 319 asthe sewing operation is being performed. Lower feed dog 312 is coupledto main drive shaft 302 through cams and linkages in a manner well knownto those skilled in the art to produce the desired oscillatory motion.

An existing Singer 300W 194 sewing machine is incapable of providing thedesired overfeed of one layer with respect to another. Upper feed dog310 moves at the same speed and distance in the feed direction 319 aslower feed dog 312 so that top layer 316 and bottom layer 318 areadvanced at precisely the same rate through the sewing area by these twofeed dogs alone. Presser foot 308 has no function in advancing layers316 and 318 through the sewing area. All of these features areconventional in the Singer 300W 194 sewing machine, and need not bedescribed in any further detail.

The present invention involves the modification of the Singer 300W 194sewing machine to incorporate upper walking foot 320 in addition topresser foot 308, upper feed dog 310, needle 306 and lower feed dog 312.Upper walking foot 320 is coupled to main drive shaft 302 by linkage 321to produce the desired motion in the feed direction 319, while upperfeed dog is coupled to presser foot 308 to produce the desired motionperpendicular to the feed direction 319. The combination of the motionproduced by linkage 321 and the perpendicular motion produced bymovement of presser foot 308 causes an elliptical pattern of movementfor upper walking foot 320. This motion produces overfeed of layer 316with respect to layer 318. Typically, although not necessarily, upperwalking foot 320 has a larger lower gripping surface 322 than either ofpresser foot 308 or upper feed dog 312. Surface 322 preferably isserrated to provide better gripping of upper layer 316.

Linkage 321 interconnecting upper walking foot 320 with drive shaft 302will now be described with particular reference to FIG. 14. Linkage 321includes arm 324, eccentric assembly 325, slide 326, shaft 332, link334, elbow 336, and slide 340. Arm 324 is coupled to drive shaft 302through a conventional eccentric assembly 325. Assembly 325 translatesrotational motion of drive shaft 302 into linear oscillatory motion ofarm 324 in a direction parallel to its direction of elongation, towardand away from shaft 302. Assembly 325 is a conventional eccentricavailable from Singer Sewing Machines as part no. 268064 and is wellknown to those of ordinary skill in the art. Further description isdeemed to be unnecessary. A peg 328 extends through arm 324 and rides inelongated opening 330 in banana slide 326. Peg 328 is movable along andwithin opening 330 in unsecured relation with respect to slide 326. Oneend of elongated slide 326 is coupled to rotatable shaft 332. Connectedto shaft 332 is one end of link 334. Coupled to the other end of link334 is one end of elbow 336. The other end of elbow 336 is coupled toupper walking foot 320. One arm 338 of elbow 336 passes through andrides within slide 340. Arm 338 is connected to link 334 at slot 342 byfollower 344 which rides up and down within slot 342 to accommodate upand down motion of elbow 336.

Slide 340 and thus elbow 336 are coupled to linkage 346 of presser foot308 by a bolt 350 or some other means which secures bracket 348 on slide340 to linkage 346. Bracket 348 includes an elongated opening whichpermits adjustment of the relative positions of slide 340 and linkage346 by loosening of bolt 350. Adjustment of slide 340 with respect tolinkage 346 or presser foot 308 adjusts the spacing of surface 322 withrespect to throat plate 314.

Connected to arm 324 at a position spaced from drive shaft 302 is anadjustment mechanism 352. Mechanism 352 pivots arm 324 about shaft 302to change the position of peg 328 within opening 330. A preferredmechanism 352 includes a servo motor 354 which is coupled to a shaft356. One end of shaft 356 is rotatably affixed to block 358 disposed onarm 324. Arm 324 slides within a hole in block 358 to accommodatemovement of arm 324 with respect to block 358. In one embodiment, shaft356 is threaded and motor 354 rotates gear 355 which rotates gear 357which has a centrally threaded hole through which shaft 356 is threadedto raise and lower shaft 356 and thus block 358. In another embodiment,motor 354 includes a spur gear (not shown) which engages notches inshaft 356 to raise and lower shaft 356. Rotation of motor 354 in onedirection pivots arm 324 about shaft 302 to raise the position of peg328 within opening 330 toward the distal end of banana slide 326 spacedfrom shaft 332. Such movement increases the speed and distance coveredby walking foot 320 in the feed direction 319. Rotation of motor 354 inan opposite direction moves peg 328 downwardly within opening 330 towardshaft 332 to decrease the speed of and distance covered by walking foot320 in the feed direction 319.

Operation of the linkage of FIG. 14 will now be described. Rotation ofdrive shaft 302 produces linear oscillatory motion of arm 324 towardsand away from shaft 302. This oscillatory motion rotates shaft 332 backand forth about its axis. Oscillatory rotation of shaft 332 producessimilar oscillatory motion of link 334 which causes arm 338 of elbow 326to slide within slide 340 back and forth parallel to the feed direction319. This motion produces corresponding motion parallel to the feeddirection 319 of upper walking foot 320. Movement of linkage 346perpendicular to the feed direction 319 produces corresponding movementof slide 340 and walking foot 320 and causes follower 344 to ride up anddown within slot 342. The combined movement parallel and perpendicularto the feed direction 319 produces a generally elliptical movement ofupper walking foot 320.

The relative movements of walking foot 320, presser foot 308, upper feeddog 310 and lower feed dog 312 will now be described with respect toFIGS. 15A, B, C and D. As already indicated, upper walking foot 320 andpresser foot 308 move up and down in synchronization. Thus, wheneverpresser foot 308 engages material layers 316 and 318, upper walking foot320 also engages layers 316 and 318. Assembly 325 is configured toproduce movement of upper walking foot 320 parallel to feed direction319 as described in FIG. 15A-D in a manner well known to those ofordinary skill in the art. As shown in FIG. 15A, as needle 306 and upperwalking foot 310 are in a raised position, presser foot 308 is in alowered position in engagement with upper layer 316. Presser foot 308holds layers 316 and 318 in a stationary condition at a point afterneedle 306, in the direction of feed 319. At the same time, upperwalking foot 320 is in engagement with upper layer 316 only and ismoving layer 316 toward presser foot 308 in the feed direction 319.Thus, upper walking foot 320 gathers or bunches layer 316 underneathupper feed dog 310, and between presser foot 308 and upper walking foot320. At this same time, lower feed dog 312 is being urged upwardly intoengagement with lower layer 318, but at this particular moment, lowerfeed dog 312 displays no movement in the direction of feed 319.Thereafter, needle 306 and upper feed dog 310 begin to move downwardlyin a direction perpendicular to the feed direction to engage layers 316and 318. Just as upper feed dog 310 engages layer 316, and just asneedle 306 begins to penetrate layers 316 and 318, presser foot 308 andwalking foot 320 move in an upwardly direction perpendicular to the feeddirection 319 away from layer 316. Thereafter, upper walking foot 320moves upwardly and to the right as shown in FIG. 15B, or in directionsperpendicular and opposite to the direction of feed 319 of layers 316and 318. In FIG. 15B, presser foot 308 is in a raised position and isnot in engagement with layers 316 or 318. At this time as shown in FIG.B, upper feed dog 310 engages layer 316 and lower feed dog 312 engageslayer 318 and needle 306 penetrates layers 316 and 318. Upper feed dog310, lower feed dog 312 and needle 306 all move in the direction of feed319 to advance both of layers 316 and 318 in the feed direction 319, tothe position shown in FIG. 15C. Thereafter, lower feed dog 312 drops outof engagement with lower layer 318 and moves to the right, or in adirection generally opposite of the feed direction 319, as shown in FIG.15D. Presser foot 308 and upper walking foot 320 lower into engagementwith upper layer 316, as shown in FIG. 15D. At the same time, feed dog310 and needle 306 are raised out of contact with layers 316 and 318.Layers 316 and 318 are again prepared for gathering of layer 316 byupper walking foot 320 as previously described with respect to FIG. 15A.

This improvement to the Singer 300W 194 sewing machine permits theoverfeed of a top layer while retaining all the advantages found in sucha machine and associated with presser foot 308, and upper and lower feeddogs 310 and 312 respectively.

The use of machine 300 to sew a side panel to a top or bottom panel of amattress sack will now be described with particular reference to FIGS.13, 15 and 16. In this operation, upper layer 316 typically is the topor bottom panel of the mattress sack, while lower layer 318 is the sidepanel. The tape edge operation is incorporated into this sewingoperation in the manner previously described with respect to the sewingmachine of FIG. 1. A binding tape 370 is fed to the sewing area througha tape folder 372 and is folded about the edges of layers 316 and 318which are to be joined in the sewing area. Sewing machine 300 then joinstape 370 to the edges of layers 316 and 318 with a so-called safetystitch. As shown in FIG. 16, walking foot 320 is aligned so that it doesnot engage tape 370 but is spaced laterally from needle 306 and upperfeed dog 310 in a direction perpendicular to the feed direction 319.Also, as shown in FIG. 16 and in FIGS. 15A-D, upper walking foot 320 isdisposed before needle 306 with respect to the feed direction 319, whilepresser foot 308 is disposed after needle 306 with respect to the feeddirection 319. Walking foot 320 is aligned with presser foot 308 in thefeed direction 319, and lower feed dog 312 is disposed directly belowneedle 306. As a result, when walking foot 320 gathers upper layer 316,as described, walking foot 320 does not correspondingly bunch tape 370.Therefore, more material in layer 316 is incorporated into the finalproduct as compared with bottom panel 318 and tape 370 to prevent theradial bunching previously described.

The amount of extra material in layer 316, or the amount of bunching, iscontrolled by mechanism 352. Typically, mechanism 352 is operated by afoot pedal or other control (not shown) in a manner well known to thoseskilled in the art. As arm 324 is pivoted in a clockwise direction aboutshaft 302, as shown in FIG. 14, to move peg 328 closer to the distal endof opening 330 and away from shaft 332, the distance between peg 328 andshaft 332 is increased, thereby increasing the angle through which slide326 pivots, and thus the angle of rotation of shaft 332. This increasedrotational angle of shaft 332 translates into greater movement of elbow326 and walking foot 320 in the feed direction 319. Since the cycle timeof walking foot 320 remains the same, this greater distance of movementalso increases the speed of movement of walking foot 320 in the feeddirection 319. This greater movement of walking foot 320 in the feeddirection 319 produces bunching, or gathering, of a greater amount ofupper layer 316 with respect to lower layer 318. Conversely, the closerpeg 328 gets to shaft 332, the smaller is the angle through which shaft332 rotates. Thus, the movement of upper walking foot 320 in the feeddirection and the amount of extra material that is bunched on layer 316with respect to layer 318 is reduced. Folded tape 370 is wrapped aboutadjacent edges of layers 316 and 318. Tape 370, layer 316 and layer 318all pass together through the sewing area, permitting needle 306 tostitch together folded tape 370 and layers 316 and 318 with a safetystitch in a manner well known to those skilled in the art.

Having thus described one particular embodiment of the invention,various alterations, modifications, and improvements will readily occurto those skilled in the art. Such alterations, modifications, andimprovements are intended to be part of this disclosure, and areintended to be within the spirit and scope of the invention.Accordingly, the foregoing description is by way of example only and islimited only as defined in the following claims and the equivalentsthereto.

What is claimed is:
 1. A method for forming a partial mattress sackhaving a first panel and a second panel to prevent radial bunching ofthe second panel after assembly of the mattress sack, the methodcomprising the steps of:feeding the first and second panels in a feeddirection into a stitcher having a sewing needle, the first panel havinga first edge length, and the second panel having a second edge lengthless than the first edge length; holding the first and second panelsimmobile at a location after the needle in the feed direction whileadvancing the first panel only in the feed direction toward the needleto gather the first panel with respect to the second panel at a positionafter the needle in the feed direction; and sewing the first panel tothe second panel.
 2. Apparatus for forming a partial mattress sackhaving a first panel and a side panel, the apparatus comprising:a sewingmachine having a needle for stitching the first panel to the side panel,the first panel and the side panel moving through the sewing machine ina feed direction; an upper feed dog configured to move in the feeddirection at a first speed; a lower feed dog configured to move in thefeed direction at the first speed; a presser foot moveable in adirection generally orthogonal to the feed direction and disposed afterthe needle in the feed direction; an upper walking foot disposed beforethe presser foot in the feed direction; and linkage producing movementof the upper walking foot in the feed direction toward the presser footat a second speed greater than the first speed.
 3. The apparatus ofclaim 2 further comprising apparatus for adjusting the speed of theupper walking foot in the feed direction.
 4. The apparatus of claim 3,wherein the apparatus for adjusting the speed oft he upper walking footcomprises:an arm connected to a main drive shaft of the sewing machinefor producing oscillatory motion; a curved slide to which a portion ofthe arm is connected at a point spaced from the main drive shaft, an endof the curved slide being connected to a second shaft for rotation ofthe second shaft, the second shaft producing motion of the upper walkingfoot in a direction parallel to the feed direction; and a servo motorfor pivoting the arm about the main drive shaft to adjust the positionof the arm with respect to the curved slide.